Audio 4:12
Low-level releases planned for Wivenhoe dam

Nance HaxtonUpdated
Tue 26 Feb 2013, 11:32 AM AEDT

The main dam that provides most of Brisbane's drinking water is full. Seqwater is planning what it describes as 'low-level releases' over the week to cope with predicted rainfalls over the catchment area.

Transcript

ELEANOR HALL: In Queensland, the main dam that provides Brisbane's drinking water is full.

Authorities are planning what they say are 'low level releases' from Wivenhoe Dam over the next few days.

But exactly how much is allowed to flow down the Brisbane River will depend on the level of rainfall.

Nance Haxton has been speaking to Mike Foster from Seqwater.

MIKE FOSTER: Look there's probably two decisions that were made yesterday. The first decision was made that we started to increase releases out of Wivenhoe Dam, just to make sure we could bring that storage level back down to that temporary full supply level of 88 per cent.

In addition, the Minister or the State Government took a decision to re-invoke the temporary full supply level for North Pine Dam, and we certainly started to release from North Pine Dam last night.

And we continued those releases overnight. North Pine Dam is now being closed off, part of the reason for that is to try and minimise the impact on the local community.

The rainfall we actually had overnight in catchment was actually quite small, so across the North Pine/Wivenhoe/Somerset, our bigger dams, we had falls between sort of five to ten millimetres, so relatively small, relatively small in-flows.

So as of this morning, Wivenhoe is back to that temporary full supply level of 88 per cent and North Pine is down to about 95 per cent. The bigger rain is certainly anticipated into today, tonight and overnight into Tuesday.

The release rate out of Wivenhoe is continuing at about the 280 (inaudible), and to give people an idea, that's about a fifth of the releases that we were doing as part of the rain down following the Australia Day weekend.

So still very low level releases through both North Pine and Wivenhoe, but certainly we'll have to watch it pretty closely as this rain event gets upon us.

NANCE HAXTON: And why is Wivenhoe reduced to that temporary full capacity, as you mentioned before?

MIKE FOSTER: Look a decision was taken by the State Government ahead of that Australia Day weekend to reduce both North Pine and Wivenhoe to a new temporary full supply level, to effectively give both those storages additional buffer zones to handle the impending event over the Australia Day weekend.

It is precautionary, it does give us a bit of extra space to play with and despite the fact that the Bureau over the weekend did in fact sort of downgrade the volumes of water expected across our Wivenhoe, Somerset and North Pine, we're still looking at sort of falls between 100 and 200 millimetres, still relatively significant.

So that extra buffer zone and extra space I guess just gives us an extra bit of ability and a bit of extra flexibility in terms of managing those dams.

NANCE HAXTON: So could there be any more releases from Wivenhoe in coming days?

MIKE FOSTER: Look Wivenhoe releases are in fact likely to continue at the current rate certainly for the remainder of this week. The big question is whether or not we have to increase those rates out of Wivenhoe, and that will really depend on the volume of the falls over the next couple of days.

And as always with rainfall, it depends on where the rain falls and the intensity of the falls, that is there's a huge difference between 200 millimetres falling over 48 hours and 200 millimetres falling over sort of two or three or four hours.

So that's what we'll, we have to wait and see and we don't get to know that until the event is effectively upon us.

NANCE HAXTON: So what reassurances can you give the Brisbane community I suppose, who are still quite nervous when they hear about possible releases from Wivenhoe Dam, given the flood events over the last couple of years?

MIKE FOSTER: Look I guess the key message at the moment is it's - the releases we're doing at the moment are very low level releases, certainly at this stage we're hoping the releases will stay around those levels.

Whether or not they have to increase will be dependent on the rainfall, but it's also to give people an idea that the actual volumes of falls over those couple of days is a little but short of the Australia Day weekend in terms of our catchment.

So I guess the message for us to the community is that certainly we're well prepared for the event that's coming in.